Signed-off-by: Andi Kleen

---
Documentation/x86_64/boot-options.txt | 5 +++++
arch/x86/mm/init_64.c | 16 ++++++++++++++++
include/asm-x86/pgtable_64.h | 7 +++++++
3 files changed, 28 insertions(+)

Index: linux/arch/x86/mm/init_64.c
================================================== =================
--- linux.orig/arch/x86/mm/init_64.c
+++ linux/arch/x86/mm/init_64.c
@@ -53,6 +53,22 @@ static unsigned long dma_reserve __initd

DEFINE_PER_CPU(struct mmu_gather, mmu_gathers);

+enum gbopt direct_gbpages __meminitdata = GBP_DEFAULT;
+
+static int __init parse_direct_gbpages(char *arg)
+{
+ if (!strcmp(arg, "off")) {
+ direct_gbpages = GBP_OFF;
+ return 0;
+ }
+ if (!strcmp(arg, "on")) {
+ direct_gbpages = GBP_ON;
+ return 0;
+ }
+ return -1;
+}
+early_param("direct_gbpages", parse_direct_gbpages);
+
/*
* NOTE: pagetable_init alloc all the fixmap pagetables contiguous on the
* physical space so we can cache the place of the first one and move
Index: linux/include/asm-x86/pgtable_64.h
================================================== =================
--- linux.orig/include/asm-x86/pgtable_64.h
+++ linux/include/asm-x86/pgtable_64.h
@@ -239,6 +239,13 @@ static inline int pud_large(pud_t pte)

#define update_mmu_cache(vma,address,pte) do { } while (0)

+enum gbopt {
+ GBP_OFF = -1,
+ GBP_DEFAULT,
+ GBP_ON
+};
+extern enum gbopt direct_gbpages;
+
/* Encode and de-code a swap entry */
#define __swp_type(x) (((x).val >> 1) & 0x3f)
#define __swp_offset(x) ((x).val >> 8)
Index: linux/Documentation/x86_64/boot-options.txt
================================================== =================
--- linux.orig/Documentation/x86_64/boot-options.txt
+++ linux/Documentation/x86_64/boot-options.txt
@@ -307,3 +307,8 @@ Debugging
stuck (default)

Miscellaneous
+
+ direct_gbpages=off|on
+ off: Do not use GB pages for kernel direct mapping.
+ on: Use GB pages if hardware supports it, but some heuristic
+ would turn them off.
--
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